The present invention relates generally to an aligning method carried out in a conveying mechanism for conveying a semiconductor wafer or the like. More specifically, the invention relates to a method for aligning the conveying position of a processing system for processing a processing object, the method being capable of rapidly aligning the conveying position of the conveying mechanism, and a processing system for processing a processing object.
In general, an apparatus for fabricating a semiconductor device has various processing apparatuses combined with each other, and is provided with a transfer mechanism for automatically delivering semiconductor wafers between the processing apparatuses and between a cassette for housing therein a large number of semiconductor wafers and the processing apparatuses. The transfer mechanism has a transfer arm portion which is capable of bending and stretching, swiveling and vertically moving, and is horizontally moved to a transfer position to convey and transfer the wafers to a predetermined position.
In this case, it is not only required to avoid the interference or collision of the transfer arm portion with other members during the movement of the transfer arm portion, but it is also required to appropriately hold wafers, which are arranged in a certain place, and convey the wafers to a target position to deliver and transfer the wafers to an appropriate place with precision within a shift quantity of, e.g., xc2x10.2 to 0.3 mm. Some of conveying paths have a transfer mechanism capable of only bending and stretching and swiveling, or a transfer mechanism capable of vertically moving in addition to the bending and stretching and swiveling.
For that reason, there is carried out an operation called a so-called teaching operation for causing a control part, such as a computer, for controlling the movement of the transfer arm portion, to learn important positions, such as places at which wafers are transferred in the conveying paths of the transfer arm portion, as position coordinates.
This teaching operation is carried out with respect to almost all cases for transferring wafers, such as the positional relationship between the transfer arm portion and a cassette vessel, the positional relationship in vertical directions between the arm portion and the cassette for taking the wafers, the positional relationship between a supporting table in a load-lock chamber and the arm portion, and the positional relationship between the arm portion of the transfer mechanism in the load-lock chamber and the supporting table in a processing apparatus, and their position coordinates are stored. Of course, all of driving systems include an encoder or the like for assigning the driving positions. As teaching methods of this type are disclosed in, e.g., Japanese Patent Laid-Open Nos. 7-193112, 9-252039 and 2000-127069.
Specifically, a certain point on the moving path of the transfer arm portion is first used as an absolute reference for obtaining the position coordinates of a place to be taught in the whole apparatus, from designed values of the apparatus, and for causing the obtained position coordinates to be inputted to and stored in the control part as temporary position coordinates to carry out a rough teaching operation. In this case, the temporary position coordinates are inputted in view of predetermined margins so that the wafers held by the arm do not interfere with other members.
Then, the transfer arm portion is driven on the basis of the temporary position coordinates while an aligning substrate of, e.g., a transparent plastic, having a shape similar to the shape of a semiconductor wafer to be conveyed is appropriately held on the arm portion. If the transfer arm portion moves to the vicinity of the supporting table, the operation of the transfer arm portion is switched to a manual operation so as to allow fine movement, and the transfer arm portion is manually operated so that the central position of the substrate which is previously marked on the surface of the substrate is coincident with the central position which is previously marked on the supporting table, while viewing from a lateral direction or a vertical direction. When both centers are coincident with each other, the coordinates are stored in the control portion as precise and appropriate position coordinates to carry out a teaching operation. In this case, there are some cases where the transfer arm portion is slowly moved to the vicinity of the supporting table from the beginning by manual operations. In the middle of the wafer conveying path, such a teaching operation is carried out by manual operation and visual observation every place to which the wafers are transferred or delivered, to align the transfer position.
In the teaching operation when wafers are conveyed and transferred from the supporting table of the processing apparatus, the substrate is arranged at an appropriate place on the supporting table by visual observation or by means of a camera mechanism as shown in Japanese Patent Laid-Open No. 7-193112, and the substrate is conveyed to the vicinity of the transfer position by means of the transfer arm portion. Then, as described above, the transfer arm portion is operated by visual operation so that the central position of the substrate is coincident with the central position of the transfer place. When both centers are coincident with each other, the coordinates are stored in the control part as appropriate position coordinates to carry out a teaching operation.
For that reason, in the above described conventional aligning method, there is a problems in that it takes a very long time since delicate alignment is carried out by swiveling and/or bending and stretching the arm while carrying out visual observation.
There is also a problem in that alignment precision is greatly varied with individual differences. Moreover, since the transfer arm portion rapidly moves in an actual operation during process, an inertia force acts thereon, so that there are some cases where a transfer position during a slow manual teaching operation is slightly shifted from a transfer position during an actual operation in which an inertia force greatly acts on the transfer arm portion.
When the transfer position is manually aligned, the transfer arm portion is delicately aligned while being moved forward and backward in the vicinity of the transfer position. On the other hand, in an actual operation during process, the transfer arm portion is not moved forward and backward, and the transfer arm portion travels in one direction to stand so that the transfer arm portion is rapidly decelerated from a rapid movement to be stopped. Therefore, there are some cases where during a teaching operation, a so-called back lash is caused in gears and so forth constituting the transfer arm portion, and this error enters the position of coordinates to cause alignment errors.
Moreover, when a plastic plate or the like is used as the aligning substrate, the weight and rigidity of the substrate are different from those of wafers. Therefore, for example, deflection is different from each other, so that there is a problem in that the transfer position is shifted.
The present invention has been made in order to effectively solve the above described problems. It is an object of the present invention to provide a method for aligning the conveying position of a processing system for processing a processing object, the method being capable of precisely and efficiently carrying out alignment during a teaching operation.
After the inventors have diligently studied an aligning method during teaching, the inventors have found that if precise alignment is carried out on a supporting table of a processing apparatus which is a final destination, even if an allowable position shift is caused on a buffer supporting table in the middle of a conveying path for semiconductor wafers, this can be ignored, and have made the present invention.
According to a first aspect of the present invention, there is provided a method for aligning a conveying position of a processing system for processing a processing object, the processing system comprising a processing apparatus which has a supporting table for supporting thereon the processing object and which serves to carry out a predetermined processing for the processing object, an orienter/positioner for detecting an eccentric quantity and eccentric direction of the processing object mounted on a reference table, and at least one transfer mechanism which is provided between the orienter/positioner and the processing apparatus, the method comprising the steps of: obtaining a position shift quantity of an aligning substrate when the transfer mechanism causes the to-and-fro conveyance of the aligning substrate between the reference table and the supporting table to return the aligning substrate, as a to-and-fro position shift quantity; obtaining a position shift quantity of the aligning substrate when the aligning substrate precisely aligned to be mounted on the supporting table is conveyed to the reference table by the transfer mechanism, as a one-way position shift quantity; and modifying an conveying position of a processing object, which is conveyed toward the supporting table by the transfer mechanism, on the basis of the to-and-fro position shift quantity and the one-way position shift quantity.
The present invention intends to allow the processing object conveyed to the top of the supporting table to precisely positioned to be conveyed when the processing object mounted on the reference table is conveyed to the supporting table by the transfer mechanism, so that the processing object can be smoothly processed in the processing apparatus by precisely positioning the processing object on the supporting table.
On the reference table, the eccentric quantity and eccentric direction of the processing object can be detected by the orienter/positioner. On the other hand, it is not easy to detect the eccentric quantity and eccentric direction of the processing object mounted on the supporting table. Therefore, according to the present invention, the position shift quantity of the aligning substrate when the transfer mechanism causes the to-and-fro conveyance of the aligning substrate between the reference table and the supporting table to return the aligning substrate is obtained as a to-and-fro position shift quantity, and the position shift quantity of the aligning substrate when the aligning substrate precisely aligned to be mounted on the supporting table is conveyed to the reference table by the transfer mechanism is obtained as a one-way position shift quantity, so that the processing object can be precisely positioned to be conveyed to the top of the supporting table.
Thus, the conveying position during the conveyance of the processing object toward the supporting table is modified on the basis of the to-and-fro position shift quantity caused when the to-and-fro conveyance of the processing object is carried out between the reference table of the orienter/positioner and the supporting table of the processing apparatus, and on the basis of the one-way position shift quantity caused when the one-way conveyance of the processing object is carried out from the supporting table toward the reference table. Therefore, it is possible to rapidly and precisely carry out a teaching operation without causing individual differences.
During alignment in the teaching operation, the aligning substrate is conveyed at the same conveying speed as that during process, and adjustment for delicately moving the aligning substrate forward and backward by manual operations is not carried out. Therefore, it is possible to precisely carry out alignment without causing position errors caused by the difference in inertia force and position errors caused by a back lash.
For example, the processing system may have a plurality of processing apparatuses, each of which is said processing apparatus, for modifying the conveying position with respect to a conveying path to each of the supporting tables.
In the above described cases, the modified quantity corresponds to a difference between the to-and-fro position shift quantity and the one-way position shift quantity.
For example, a plurality of transfer mechanism may be provided between the orienter/positioner and each of the processing apparatus, and a buffer supporting table for causing the processing object to be standby on the way may be provided therebetween, the aligning substrate being conveyed by means of the plurality of transfer mechanisms and the buffer supporting table.
Thus, even if the plurality of transfer mechanisms and buffer supporting tables are associated with each other to be provided in the middle of the conveying paths, it is not required to carry out alignment on each of the buffer supporting tables, so that it is possible to greatly shorten the time required to carry out alignment in the teaching operation.
For example, an actual processing object is used as the aligning substrate.
Thus, since the actual processing object is used unlike the conventional case where the plastic plate or the like is used as the aligning substrate, the thickness, dimension and rigidity are the same as those of the processing object during process. Therefore, the deflection quantity and so forth during alignment in the teaching operation are the same, so that it is possible to more precisely carry out alignment.
According to a second aspect of the present invention, an apparatus for carrying out the method according to the present invention is provided. That is, the processing system comprises: a processing apparatus which has a supporting table for supporting thereon a processing object and which serves to carry out a predetermined processing for the processing object; an orienter/positioner for detecting an eccentric quantity and eccentric direction of the processing object mounted on a reference table; at least one transfer mechanism which is provided between the orienter/positioner and the processing apparatus; and a control part for controlling the transfer mechanism and the orienter/positioner, wherein the control part obtains a position shift quantity of the aligning substrate when the transfer mechanism causes the to-and-fro conveyance of the aligning substrate between the reference table and the supporting table to return the aligning substrate, as a to-and-fro position shift quantity, and obtains a position shift quantity of the aligning substrate when the aligning substrate precisely aligned to be mounted on the supporting table is conveyed to the reference table by the transfer mechanism, as a one-way position shift quantity, the control part modifying an conveying position of a processing object, which is conveyed toward the supporting table by the transfer mechanism, on the basis of the to-and-fro position shift quantity and the one-way position shift quantity.
In this case, for example, a plurality of processing apparatus, each of which is said processing apparatus, are provided, and the transfer mechanism comprises: a common conveying mechanism which is commonly used for each of the processing apparatuses; and separate transfer mechanisms, each of which is provided so as to correspond to each of the processing apparatuses, each of the separate transfer mechanisms being provided with a buffer supporting table for temporarily supporting thereon the processing object.